Use Of Nitrification Inhibitors Research Articles

Assessing the long-term impact of urease and nitrification inhibitor use on microbial community composition, diversity and function in grassland soil

Reductions in ammonia (NH3) and nitrous oxide (N2O) emissions from agricultural systems are critical for achievement of sustainability targets that underpin international efforts on climate and biodiversity. Urease inhibitors (UI) such as N-(n-butyl) thiophosphoric triamide (NBPT) and nitrification inhibitors (NI) such as dicyandiamide (DCD) slow down microbial and chemical N transformation rates in soil, resulting in decreased environmental N losses. To date there has been minimal assessment of the long-term non-target impacts of UI and NI on soil microbial communities and biological function in grasslands. Utilising a temperate grassland field experiment where fertilisers (with or without inhibitors) were repeatedly applied over a five year period, we assessed the impact of individual or combined inhibitor use on microbial community composition, abundance and function via a combination of functional assays, quantitative polymerase chain reaction (qPCR) assays and amplicon sequence analysis. We also investigated the effect of N inhibitor use on the N functional community, and whether the form of applied N fertiliser (i.e. calcium ammonium nitrate (CAN) or Urea) affected microbial community composition and function. Treatments included a Control (no N); CAN; Urea; Urea + NBPT (UI); Urea + DCD (NI); and Urea + DCD + NBPT (NI & UI). There was no impact of either UI or NI use on non-target microbial community composition or abundance. Function and the abundance of N cycling communities were mainly unaffected by fertilisation or the use of inhibitors. The observed effect of NI was primarily on the nitrification process. There was a significant reduction in nitrification potential associated with the use of NI, and in the case of the Urea + DCD treatment a reduction in COMAMMOX nitrifier abundance, and an increase in potential N mineralisation and N2O emissions. Finally, there was a significant impact of fertilisation and fertiliser type (i.e. CAN or Urea) on the fungal community structure but no impact on bacterial community structure. These results provide a knowledge base that will inform policy regarding the utilisation of N inhibitors as a mitigation measure for reducing gaseous N losses in grasslands.

Potential for the adoption of measures to reduce N2O emissions from crop residues in Denmark

Crop residues represent a climate change dilemma: they can promote carbon (C) sequestration, but they may also stimulate emissions of the powerful greenhouse gas nitrous oxide (N2O). Although there are crop residue management measures to reduce N2O emissions, N2O reductions achieved at national scale with these measures have been seldom studied, and how farmers' willingness to accept the measures constrains their potential remains largely unknown. Using Denmark as a case study, we combined a survey (completed by 592 farmers) and national data to assess the practical potential and obstacles for the successful implementation of management strategies to reduce N2O emissions from crop residues. Crop residue removal (particularly from vegetables and cover crops) and nitrification inhibitors were identified as effective in reducing N2O emissions from a biophysical perspective. If all aboveground crop residues from vegetables and cover crops were removed, N2O emissions could be reduced by 0.181 Gg N2ON, corresponding to 11% of the total N2O emissions from crop residues nationally. However, a low percentage of farmers would be willing to remove crop residues from the field, especially for vegetables and cover crops (25%), in connection to the possible short- to medium-term reduction in C sequestration. Similarly, use of nitrification inhibitors would reduce emissions by 0.247 Gg N2ON, corresponding to 15% of the total residue N2O emissions, and only 37% of all farmers would accept their use. Our results highlight that farmer’ preferences for the adoption of measures can constrain the use of the few available effective mitigation options. Better knowledge dissemination and advisory services are crucial to address this challenge; farmers may be motivated to remove aboveground crop residues by highlighting the proportionally more important contribution of belowground residues to C sequestration, and that aboveground residues may have commercial value (biorefining, biogas, biofuel), although these options need further development.

Use of Symbiotic Fungi to Reduce the Phytotoxic Effect of DCD Nitrification Inhibitors in Lettuce

Nitrification inhibitors are commonly used to prevent nitrate leaching. However, the use of nitrification inhibitors is not free of side-effects. Some may be absorbed by the plant and cause phytotoxicity or even affect the food chain. Therefore, a solution that limits the absorption of nitrification inhibitors and its accumulation by the plant may mitigate health and environmental issues potentially associated with high levels of nitrification inhibitors. This solution may relay in the modulation of the plant’s metabolism through the interaction with specific fungal partners. This work tested the hypothesis that the symbiotic interaction between fungi and plant roots can reduce the destructive effects of the nitrification inhibitor Dicyandiamide (DCD) in plants by reducing the uptake of nitrification inhibitors. A greenhouse experiment was conducted, using a complete randomized block design, to test the effect of symbiotic fungi (plants inoculated with Piriformospora indica, Glomus etunicatum, and Glomus mosseae and noninoculated) on the phytotoxicity of DCD applied at four concentrations (0, 5, 50, and 100 mg kg−1 soil). Latuca sativa, cultivar Siyahoo, was selected for this experiment due to its economic value all over the world. The use of high DCD concentrations (100 mg kg−1 soil) affected the leaf chlorophyll content and plant growth in a manner that was significantly mitigated by the symbiosis of the plant with the fungal partner. These results highlight the benefits of using symbiotic fungal inoculants as plant protectors against the phytotoxic effects of DCD.

Site-specific nutrient management in rice (Oryza sativa): Status and prospect–A review

Site-specific nutrient management (SSNM) plays a vital role in increasing crop profitability, maintaining soil health and reducing environmental pollution. Field experiments and demonstrations conducted across southeast (SE) Asia were conducted during 2020–21 at ICAR-Indian Agricultural Research Institute, New Delhi and observed that SSNM includes various nutrient management practices and each practice have a positive impact on fulfilling its vital role. After a thorough study, this review reflects that fertilizer recommendations based on targeted yield concept were more balanced, profitable and helpful in controlling soil nutrient mining and essential for sustainable crop production. Establishment of an attainable yield target, based on location, season, climate, rice cultivar and crop management ensures effective use of existing indigenous nutrients such as from soil, organic amendments, crop residue, manure and irrigation water and application of fertilizer to dynamically fill the deficit between crop needs and indigenous supply and to maintain soil fertility. Moreover, use of nitrification inhibitor, deep placement of nitrogen (N) and NPK fertilizers reduces the loss of N fertilizers up to 20% and increases rice yield up to 10%. The leaf colour charts (LCC), chlorophyll meter or SPAD are inexpensive need based tools for fertilizer N management that can reduce the excessive application of N (10–50%). Optical sensor-based nitrogen management is an alternative to LCC and SPAD that can quickly and reliably monitor N requirements of rice. On the other hand, the dissemination of SSNM through LCC, SPAD, QUEFT models, optical sensor etc., requires training of researchers, local extension workers, fertilizer retailers, and farmer leaders on techniques and guidelines for enabling rice farmers. Therefore, a simple nutrient decision support tool, Nutrient Expert® (NE) is useful to develop strategies to manage fertilizer N, P and K tailored to farmer’s field or growing environment. However, comparative evaluation of different SSNM approach is essential for location wise fertilizer prescription for increasing crop profitability, soil health and environmental safety.

Nutritional, Physiological, and Morphological Effects on Almond Trees Grown by Fertigation with the Nitrification Inhibitor 3, 4-DimethylpyrazoleSuccinic Acid

Nitrogen fertilization is key to improve crop yield. However, due to the harmful environmental effects of fertilizers, farmers and governments are searching agronomic practices that provide nutrients to the crops with minimal environmental impact, as for example the use of nitrification inhibitors. These compounds act on ammonium reducing its oxidation to nitrate, and soil´s nitrogen remains longer in the form of ammonium helping prevent nitrate lixiviation. The objective of the experiment was to evaluate the effect of a new nitrification inhibitor (DMPSA) in almond trees. We studied the effect of three solutions on vegetative growth, nutrition, and physiology on Alvijor almond plants irrigated with one of three possible study solutions i) 3:1 nitrate:ammonium rate solution ii) 1:1 nitrate:ammonium rate solution, or iii) 1:1 nitrate:ammonium rate solution plus a nitrification inhibitor (3,4-dimethylpyrazolesuccinic acid). Plants were grown in a greenhouse in calcareous and alkaline soil from the Spanish Levante area. Macro and micronutrients were determined from drainage samples collected throughout the experiment. At the end of the experiment, gaseous exchange and chlorophyll fluorescence parameters were measured and plants harvested to analyse morphological characteristics (leaf, stem and root fresh and dry weight, aerial part rate, and trunk diameter) and N, P, K, Ca, and Mg content in the leaves. We found higher levels of ammonium and lower nitrates in the roots and higher vegetative growth with the irrigation solution containing the nitrification inhibitor in comparison with treatment solutions 1:1 and 3:1. The drainage showed that NI reduces the level of nitrates in the leachate, limiting its discharge to the subsoil. In conclusion, the nutrient solution with the nitrification inhibitor has a positive impact on Alvijor almond plants and the environment.

Preferential mineral N form uptake by sugarcane genotypes contrasting in nitrogen use efficiency

Summary Ammonium has been reported as a ‘preferred’ nitrogen (N) source for sugarcane (Saccharum spp.), which can improve N use efficiency (NUE) in this crop. We aimed to evaluate the preferential uptake of ammonium and nitrate in sugarcane genotypes contrasting with NUE under controlled conditions. Four sugarcane genotypes previously selected by another experiment (ER: efficient and responsive; ENR: efficient and nonresponsive; IR: inefficient and responsive; INR: inefficient and nonresponsive) were grown in a growth chamber and fertilized with two 15N-labeled forms [(NH4)2SO4 (15N-NH4+) or KNO3 (15N-NO3−)]; soil was used as substrate. Plants were evaluated at three time points: 0, 24, and 72 h after 15N-fertilization. For the efficient genotypes (ER and ENR), the soil NH4+ levels were about 20% lower than those found for the inefficient genotypes (IR and INR) indicating greater N extraction by the plant. Nitrogen derived from fertilizer (NDFF) and 15 N recovery from fertilizer (15N RFF) in roots were influenced by the genotypes, in which responsive genotypes (ER and IR) presented a mean value 40% higher than the genotype INR, showing that greater absorption is more related to response than efficiency. Three days after N application, NDFF and 15N RFF from 15N-NH4+ were greater than 15N-NO3− in 40% and 65% for the roots and aerial part, respectively. The results of this study confirmed that sugarcane presents preferential uptake of NH4+ N form 3 days after fertilization. The use of nitrification inhibitors can be considered for providing a longer NH4+ residence time in the soil, also contributing to augmenting the NUE in sugarcane.

Assessing the Long-Term Impact of Urease and Nitrification Inhibitor Use on Microbial Community Composition, Diversity and Function in Grassland Soil

Assessing the Long-Term Impact of Urease and Nitrification Inhibitor Use on Microbial Community Composition, Diversity and Function in Grassland Soil

Nitrification inhibitor 3,4-Dimethylpyrazole phosphate improves nitrogen recovery and accumulation in cotton plants by reducing NO3− leaching under 15N-urea fertilization

PurposeThe use of nitrification inhibitors could be an interesting alternative when applied to enhance nitrogen (N) fertilizer use efficiency in annual crops such as cotton under tropical soil conditions. Thus, our aim was to evaluate the efficiency of the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) in a typical tropical soil by evaluating the fate of nitrogen (N-NO3−, N-NH4+ and total N in soil and leached water), N accumulation and N recovery by cotton plants and soil.MethodsLeaching columns with cotton plants were used to assess N-NO3− and N-NH4+ losses in drainage water. The treatments consisted of three N levels applied in side-dressing (corresponding to 50, 100 and 150 kg N ha−1) as 15N-urea with and without DMPP application. An additional treatment (absence of N application in side-dressing) was used as a control.Results3,4-Dimethylpyrazole phosphate efficiently improved N recovery after urea fertilizer was applied to plants and in the soil by reducing NO3− leaching, leading to enhanced N acquisition from fertilizer and soil and augmenting N accumulation in plants, mainly when high N levels above 100 kg N ha−1 were applied. We found that total N recovery increased 31% when 150 kg N ha−1 was applied as a urea + DMPP source compared to the application of conventional urea. In addition, DMPP application reduced NO3− leaching losses (by approximately 11 to 20%), although it had no significant effect on the shoot or root dry matter yields.ConclusionThe reduction in NO3− leaching losses obtained herein highlights the potential of DMPP to mitigate the impact of increased urea inputs on leaching losses, thereby improving N use efficiency and N uptake in cotton crops.

Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land-applied manure.

Manure application to land and deposition of urine and dung by grazing animals are major sources of ammonia (NH3 ) and nitrous oxide (N2 O) emissions. Using data on NH3 and N2 O emissions following land-applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed, and the effects of mitigation strategies were evaluated. The NH3 data represent emissions from cattle and swine manures in temperate wet climates, and the N2 O data include cattle, sheep, and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH3 EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH3 -N kg-1 total N (TN), respectively, whereas the NH3 EF of broadcast swine slurry was 0.29. Emissions from both cattle and swine slurry were reduced between 46 and 62% with low-emissions application methods. Land application of cattle and swine manure in wet climates had EFs of 0.005 and 0.011 kg N2 O-N kg-1 TN, respectively, whereas in dry climates the EF for cattle manure was 0.0031. The N2 O EFs for cattle urine and dung in wet climates were 0.0095 and 0.002 kg N2 O-N kg-1 TN, respectively, which were three times greater than for dry climates. The N2 O EFs for sheep urine and dung in wet climates were 0.0043 and 0.0005, respectively. The use of nitrification inhibitors reduced emissions in swine manure, cattle urine/dung, and sheep urine by 45-63%. These enhanced EFs can improve national inventories; however, more data from poorly represented regions (e.g., Asia, Africa, South America) are needed.

Gross Ammonification and Nitrification Rates in Soil Amended with Natural and NH4-Enriched Chabazite Zeolite and Nitrification Inhibitor DMPP

Using zeolite-rich tuffs for improving soil properties and crop N-use efficiency is becoming popular. However, the mechanistic understanding of their influence on soil N-processes is still poor. This paper aims to shed new light on how natural and NH4+-enriched chabazite zeolites alter short-term N-ammonification and nitrification rates with and without the use of nitrification inhibitor (DMPP). We employed the 15N pool dilution technique to determine short-term gross rates of ammonification and nitrification in a silty-clay soil amended with two typologies of chabazite-rich tuff: (1) at natural state and (2) enriched with NH4+-N from an animal slurry. Archaeal and bacterial amoA, nirS and nosZ genes, N2O-N and CO2-C emissions were also evaluated. The results showed modest short-term effects of chabazite at natural state only on nitrate production rates, which was slightly delayed compared to the unamended soil. On the other hand, the addition of NH4+-enriched chabazite stimulated NH4+-N production, N2O-N emissions, but reduced NO3−-N production and abundance of nirS-nosZ genes. DMPP efficiency in reducing nitrification rates was dependent on N addition but not affected by the two typologies of zeolites tested. The outcomes of this study indicated the good compatibility of both natural and NH4+-enriched chabazite zeolite with DMPP. In particular, the application of NH4+-enriched zeolites with DMPP is recommended to mitigate short-term N losses.

Nitrification inhibitor nitrapyrin does not affect yield-scaled nitrous oxide emissions in a tropical grassland

Urea is the most common nitrogen (N) fertilizer used in the tropics but it has the risk of high gaseous nitrogen (N) losses. Use of nitrification inhibitor has been suggested as a potential mitigation measure for gaseous N losses in N fertilizer-applied fields. In a field trial on a tropical Andosol pastureland in Costa Rica, gaseous emissions of ammonia (NH3) and nitrous oxide (N2O) and grass yield were quantified from plots treated with urea (U; 41.7 kg N ha–1 application–1) and urea plus the nitrification inhibitor nitrapyrin (U + NI; 41.7 kg N ha–1 application–1 and 350 g of nitrapyrin for each 100 kg of N applied) and control plots (without U and NI) over a six-month period (rainy season). Volatilization of NH3 (August to November) in U (7.4% ± 1.3% of N applied) and U + NI (8.1% ± 0.9% of N applied) were not significantly different (P > 0.05). Emissions of N2O in U and U + NI from June to November were significantly different (P < 0.05) only in October, when N2O emission in U + NI was higher than that in U. Yield and crude protein production of grass were significantly higher (P < 0.05) in U and U + NI than in the control plots, but they were not significantly different between U and U + NI. There was no significant difference in yield-scaled N2O emission between U (0.31 ± 0.10 g N kg–1 dry matter) and U + NI (0.47 ± 0.10 g N kg–1 dry matter). The results suggest that nitrapyrin is not a viable mitigation option for gaseous N losses under typical N fertilizer application practices of pasturelands at the study site.

Analytical pitfalls when using inhibitors in specific nitrification assays

Environmental context Specific inhibitors of biological reactions in the nitrogen cycle can be used to determine the origin of reactive nitrogen species; these nitrogen species potentially degrade water quality or influence climate. However, inhibitors can potentially interfere with methods for the analysis of stable isotope ratios and concentrations of ammonium, nitrite and nitrate. The effect of this interference on several commonly used methods was investigated. These findings should help avoid the use of inappropriate analytical methods and improve data quality in studies of the nitrogen cycle. Abstract Characterisation of the reaction steps involved in nitrification can help determine the processes that produce potentially harmful environmental pollutants such as nitrite, nitrate and nitrous oxide (N2O). The use of nitrification inhibitors can uncouple the reactions and therefore assist in their mechanistic and isotopic characterisation. However, nitrification inhibitors can interfere with the methods for determining the concentrations and stable isotope ratios of ammonium, nitrite and nitrate. The interference of allylthiourea, hydrazine or sodium chlorate in colorimetric methods and stable isotope measurements were assessed. Ammonium concentrations were measured with the salicylate method. Nitrite and nitrate were measured with the Griess reaction, with nitrate first being reduced to nitrite with vanadium (III) chloride. For the stable isotope analysis, nitrite was reduced to N2O in a 1 : 1 sodium azide and acetic acid buffer solution; preceded, when necessary, by ammonium oxidation to nitrite by hypobromite or nitrate reduction to nitrite on an activated cadmium column. Sodium chlorate did not interfere with any of the analyses and none of the inhibitors interfered with the stable isotope ratios determination of nitrate. Allylthiourea interfered with ammonium and nitrate quantification. Both allylthiourea and hydrazine also clearly interfered in the determination of the nitrogen stable isotope ratio of ammonium, while only allylthiourea interfered in the determination of nitrogen and oxygen stable isotope ratios of nitrite. Although we suggest methods to overcome some of these interferences, our study demonstrated that the analytical methods used in combination with allylthiourea or hydrazine as nitrification inhibitors should be considered with caution when designing experiments.

Site-specific Nutrient Management for Enhancing Crop Productivity

Nutrient management plays a crucial role in achieving self-sufficiency in food grain production. High price index of chemical fertilizers coupled with mount pollution problem gave rise to interest in precision nutrient management tools. Site specific nutrient management (SSNM) increases and maintains the yield by optimizing the balance between supply and demand of nutrients. Nutrient application as per SSNM concept resulted in significantly higher grain yields of maize, rice, wheat and other important crop over recommended dose of fertilizers (RDF) and farmer’s fertilizers practices. The SSNM is real time feeding of crops with nutrients while recognizing the inherent spatial variability which enhances crop productivity, nutrient use efficiency (NUE) and avoids nutrient wastage. For effective SSNM, utilization of different sensing devices of soil and plant nutrient status, decision support systems, GIS, remote sensing, simulation models and nenoparticles play an important role. Traditional techniques like balanced fertilization, use of nitrification inhibitors and slow-release nitrogenous fertilizers (SRNF) are also used to attain higher productivity and reduce environmental pollution. This paper deals with the SSNM approaches which are able to enhance crop productivity, NUE and sustainability.

Effects of commonly used nitrification inhibitors—dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and nitrapyrin—on soil nitrogen dynamics and nitrifiers in three typical paddy soils

The use of nitrification inhibitors (NIs) with ammonium (NH4+) -based fertilizers is an efficient strategy for reducing nitrogen (N) loss by affecting ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in agricultural soils. The inhibition mechanisms of NIs on AOA and AOB are still debated, as some studies have demonstrated that NIs inhibited functionally dominant groups, while others have reported selective inhibition of AOB rather than AOA. Here, we identified the impacts of the most commonly used NIs (dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP) and nitrapyrin) on the nitrification activity, N2O emission, and abundance and metabolic activity of ammonia oxidizers (AOA, AOB, and comammox (detected only in HL)) in three paddy soils (HL, JX, and SC) with distinct properties using microcosm incubation combined with the 13CO2-DNA-stable isotope probing (SIP) technique. Most of the NIs treatments effectively inhibited the N2O emission with efficacy suppressed the metabolic activity of AOB, regardless of soil type and NI type, whereas the nitrification process and AOA activity could not be inhibited. The efficacy of NIs was also dependent on soil chemical properties, as nitrapyrin did not inhibit AOB growth at the beginning of microcosm incubation in HL, and DCD successfully inhibited the activity of both AOA and AOB in JX. In HL, DCD and DMPP effectively inhibited the activity of comammox, while nitrapyrin could not inhibit its activity. This study is the first to identify the response pattern of comammox to DCD, DMPP, and nitrapyrin in paddy soil by DNA-SIP microcosm incubation. This study also suggested that NIs might selectively inhibit AOB rather than AOA.

Effects of Different Chabazite Zeolite Amendments to Sorption of Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP) in Soil

Application of natural zeolitites (ZTs, rock with > 50% of zeolites) as a soil amendment is recognized as a suitable method for increasing substrate quality. ZT is used at natural state or pre-enriched with specific cations (e.g., NH4+) to slow-release nutrients. ZT at natural state has been shown to mitigate gaseous N losses and favor crop yield, while NH4-enriched ZT has been reported to show quick NO3− production and relatively high gaseous N losses. The use of nitrification inhibitors (NIs) could alleviate these losses. In this work, the sorption behavior of a synthetic NI 3,4-dimethylpyrazole phosphate (DMPP) on different soil-ZT mixtures as well as on pure ZTs (natural and NH4-enriched) was tested. High sorption of NI can reduce its inhibitory effects and consequently the nitrogen use efficiency (NUE). Results show that natural ZTs had a deficient capacity for DMPP sorption and thus decreased the possibility to retain DMPP once applied to the soil. The sorption capacity strongly positively correlated to soil organic C content, supporting that sorption was mainly driven by soil organic matter. Any types of ZT added to the soil, notably that at natural state, have decreased the potential sorption of DMPP principally because of a dilution of the total organic C which reduced substrate hydrophobicity. A lower DMPP sorption in the substrate can mean higher availability of DMPP to soil microbial biomass and thus a higher potential in inhibiting nitrification. These beneficial effects may result in an advantageous strategy for increasing NUE.

Biochar counteracts nitrification inhibitor DMPP-mediated negative effect on spinach (Spinacia oleracea L.) growth.

The use of nitrification inhibitors (NIs) such as 3,4-dimethylpyrazole phosphate (DMPP) has been suggested to diminish agricultural soil nitrate (NO3-) loss and increase nitrogen (N) use efficiency (NUE). However, the yield of ammonium (NH4+)-sensitive plants such as spinach (Spinacia oleracea L.) may be adversely affected by the application of NIs at high N levels and, on the other hand, the efficiency of the NIs may also be affected by soil amendments such as biochar. These two issues are still not adequately addressed. The aim of this study was to evaluate the effect of different N levels including DMPP or not in a calcareous soil with and without amendment of wheat straw biochar on spinach yield, NUE, nitrate concentration of spinach leaf, activity of enzymes nitrate reductase (NR) and nitrite reductase (NiR), and soil ammonium (NH4+) and NO3- concentration under greenhouse conditions. This experiment was carried out with different N rates factor at seven levels (un-fertilized, N0; fertilized with 50mgN kg-1 soil, N50; fertilized with 75mgN kg-1 soil, N75; fertilized with 100mgN kg-1 soil, N100; fertilized with N50+DMPP; fertilized with N75+DMPP; and fertilized with N100+DMPP) and biochar (BC) factor at two levels (0, 0%BC; and 2% (w/w), 2%BC) with six replications over a 56-day cultivation period of spinach. Results showed that the application of DMPP had no significant effect on the yield of spinach plant at low and medium levels of N (50 and 75mgN kg-1 soil), but decreased the yield of this plant at the higher level of N (100mgN kg-1 soil). However, application of BC decreased the negative effect of DMPP on spinach yield as the yield in spinach plants fertilized with N75+DMPP and N100+DMPP significantly increased. Both application of DMPP and addition of BC to soil decreased leaf NO3- concentration by 29.2% and 16.3% compared to control, respectively. Biochar compared to control decreased NR activity by 46.3%. With increasing N rate, NR and NiR activities increased, but DMPP decreased the activities of both enzymes. Biochar reduced the efficiency of DMPP as soil NH4+ concentration was higher in the treatments containing DMPP without BC at 56 days after planting. Biochar and DMPP could increase the quality of spinach plant through decreasing the leaf NO3- concentration. In general, wheat straw biochar counteracted DMPP-mediated negative effect on growth of spinach plant at high level of N by decreasing the efficiency of this inhibitor. These results provide the useful information for managing the application rate of N fertilizers including DMPP in biochar-amended soil.

Use of urease and nitrification inhibitors to reduce gaseous nitrogen emissions from fertilizers containing ammonium nitrate and urea

Nitrogen (N) fertilizers increase agricultural yields, but also lead to the release of the greenhouse gases nitrous oxide (N2O) and ammonia (NH3). This not only reduces the efficiency of N use, but also results in climate change and loss of biodiversity. The use of nitrification inhibitors may improve the efficiency of N use and reduce the emission of greenhouse gases. We tested three inhibitors (NZONE MAX, Piadin and N-(n-butyl) thiophosphoric triamide (NBPT)) added to two common N fertilizers (urea and urea ammonium nitrate (UAN)) and determined emissions of CO2, N2O and NH3 to evaluate the effectiveness of these three inhibitors and to improve our understanding of the soil nitrogen cycle. NBPT effectively reduced NH3 volatilization by 50% (from 3.0 g NH3-N m−2 in urea alone to 1.4 g NH3-N m−2 in urea + NBPT). Piadin decreased N2O emissions (from 0.98 g N2O-N m−2 in urea alone to 0.15 g N2O-N m−2 in urea + Piadin and from 0.81 g N2O-N m−2 in UAN alone to 0.39 g N2O-N m−2 in UAN + Piadin) by inhibiting the conversion of NH4+ to NO3−. However, although Piadin was found to be an effective nitrification inhibitor, the risk of higher NH3 emissions (from 3.0 g NH3-N m−2 in urea alone to 4.5 g NH3-N m−2 in urea + Piadin) with the addition of Piadin cannot be neglected in environmental and economical evaluations.

Methane and nitrous oxide productions affected by natural nitrification inhibitors under different soil types

Inefficient used of urea fertilizer contributes to producing methane (CH4) and nitrous oxide (N2O) emissions. One of the options to mitigate CH4 and N2O emissions is through the use of nitrification inhibitors (NI). The objective of this study was to evaluate the effectiveness of some plant-based NI (NNI) on CH4 and N2O production under two different soils types. An incubation experiment was arranged using 2 x 3 x 3 factorial designs. All treatments were conducted with three replicates. The first factors were paddy soils (Inceptisols and Vertisols), the second were NNI (coconut husk, coffee waste, and Ageratum conizoides) and the third were the rate of the NNI (10, 20 and 30 ppm). The results showed that CH4 production was found lowest at the rate of 30 ppm of coconut husk application. Coconut husk at the rate of 20 ppm produced the lowest N2O production. Based on the global warming potential (GWP), the lowest production was the application of Ageratum conizoides at the rate of 30 ppm. Applying a higher rate of natural NI resulted in lower productions of CH4 and N2O. Chemical contents of natural NI influenced microbial activities that produce CH4 and N2O through nitrification and denitrification processes.

Conversion of ammonium to nitrate and abundance of ammonium-oxidizing-microorganism in Tropical soils with nitrification inhibitor

The use of nitrification inhibitors (NIs; dicyandiamide - DCD) is an alternative to reduce oxidation of ammonium (NH4 +-N) to nitrate (NO3 – -N) in the soil, reducing NO3 – -N losses from fertilization practices. Based on the hypothesis that DCD reduces conversion of NH4 +-N to NO3 – -N in tropical soils and inhibits ammonia oxidizing microorganisms (AOM) abundance, soils from the Piracicaba region, Sao Paulo, with different textures (sand, loam and clay) were incubated with ammonium sulphate (AS) and DCD. Contents of NH4 +-N, NO3 – -N, soil pH, and AOM abundance were quantified periodically. Ammonium sulphate increased AOM abundance in all soils, but AS+DCD presented AOM abundances similar to the control. During 90 days of incubation, the effectiveness of DCD in reducing NO3 – -N production was 1.8, 86.4, and 145.6 mg kg–1, while the effectiveness of DCD in reducing AOM abundance was 1.2, 3.0 and 2.3 × 10–3 g soil–1 for sandy, loamy, and clayey soils, respectively. DCD effectiveness was greater in loamy and clayey soils due to the naturally low nitrification in sandy soils. Application of AS treated with DCD showed potential not only to reduce NO3 – -N production in loamy and clayey soils, but also to decrease the soil nitrification rate. Overall, DCD was effective in reducing AOM abundance and conversion of NH4 +-N to NO3 – -N in loamy and clay soils evaluated here. The increase in clay content directly influences DCD effectiveness in reducing conversion of NH4 +-N to NO3 – -N.

Evaluating the ecotoxicity of nitrification inhibitors using terrestrial and aquatic test organisms

BackgroundThe increasing demand for food and animal fodder worldwide has led to an intensified agriculture with an increasing use of nitrogen fertilizers. More recently, nitrate leaching and gaseous nitrogen emissions have become the focus of environmental discussions and climate politics. One approach to reduce such negative impacts is the use of nitrification inhibitors (NIs) that have shown to effectively reduce nitrogen losses to the groundwater and the air. However, ecotoxic effects of NIs have been studied to a limited extent only. Therefore, two commercial NIs (Piadin and Vizura) and an active ingredient of another NI, dicyandiamide (DCD), were assayed using various ecotoxicological biotests and test species: the Lemna Growth Inhibition Test (Lemna gibba), the Seed Germination/Root Elongation Toxicity Test (Agrostemma githago, Fagopyrum esculentum, Glycine max, Hordeum vulgare, Lunaria annua, Zea mays), the Seedling Emergence and Seedling Growth Test (A. githago, F. esculentum, Z. mays) and the marine Luminescent Bacteria Test (Aliivibrio fischeri). The fresh water L. gibba and the bacterium A. fischeri were exposed to different test concentrations in liquid growth media, whereas the terrestrial plants were exposed to the test substances diluted/dissolved in deionized water and added to the solid growth medium.ResultsDicyandiamide did not show ecotoxic effects in any test conducted. Piadin and Vizura showed ecotoxic effects throughout all experiments. Frond number and frond area of L. gibba were inhibited with increasing concentrations of both substances with Piadin leading to an earlier inhibition and therefore lower EC50 values. In the Seed Germination Test, Vizura generally inhibited seed germination and root development more effectively than Piadin. Regarding both substances, the endpoint root length was much more sensitive than the endpoint germination. In the Seedling Emergence Test, Z. mays was the least sensitive and the rare weed species A. githago the most sensitive species with regard to the tested endpoints and both substances. A. fischeri was strongly inhibited by Vizura, whereas Piadin had barely effects on the bacteria.ConclusionAll findings indicate ecotoxic effects of Piadin and Vizura, especially on the aquatic species L. gibba and on the root development of several terrestrial plant species. However, the origins of the ecotoxic properties remain unclear as both substances contain a mixture of—to some extent unknown—chemical compounds.